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What is a raw data takeoff and is there a benefit to performing them?
I heard a pilot mention a raw data takeoff in offhand conversation. The topic was generally about maintaining hand flying skills. What exactly is a raw data takeoff and is there a benefit to a pilot's flying skills from practicing them?

Raw data means data read on the basic instruments. Not-raw data means enhanced information built from raw data and/or flight management system.
Flight director bars are not raw data, but a computation from basic air data, desired airspeed, roll angle limit, etc. At the next higher level, the autopilot can use the FD data to fly the aircraft. Similarly desired speed can be determined automatically and thrust can be managed by the auto-throttle.
Taking off and climbing with FD, auto-throttle and autopilot

Takeoff with FD and AP, just after liftoff (A320 simulator). Source: Youtube
The green bars of the FD shows what should be the attitude of the aircraft, SRS (speed reference system) guidance law has been used to determine the desired 165 kt speed. The pilot may fly the aircraft manually using these non-raw data.
In the present case the pilot has also activated another layer of assistance: Autopilot and auto-throttle. The AP follows the FD indications, and the thrust is managed by the auto-throttle so that the desired speed is achieved safely as soon as possible.
The indication in the top-left corner means autopilot, flight director and auto-throttle are currently selected / active.
T/O with raw data
Flying with raw data implies not using the FD or the SRS mode, nor the AP other modes or the auto-throttle.
The crew must determine the attitude to be used after the T/O rotation, and during the climb. They also need to manage the thrust required. For example, the roll angle has to be determined manually, depending on all factors discussed above and the desired horizontal track.

Takeoff without FD (A320). Source: Youtube
Benefits
Not using computer assistance helps maintaining and developing pilot skills and prevents dependency on automation that can always fails. The correct attitude, speed and thrust depend on many limits  — some are displayed in the speed indicator band and the attitude indicator when they have video displays — that the pilots must have in mind.
So it's usual that pilots perform manual take-offs and landings and raw-data operations. The frequency of such permanent training may be influenced by the company rules (standard operating procedures, SOP) which can either encourage or discourage crews to use the airplane automatic features at certain phases of the flight.
On modern aircraft there are some mechanisms can't be inactivated as the direct transmission between controls and corresponding actuators have been replaced, partially or totally, by electrical links. The conversion between actual pilot movements and electrical command signals is subject to some level of filtering provided by the fly-by-wire system.
Other raw data operations

Raw data (ILS) approach.
Raw data navigation.

This post consistently uses Airbus-based explanations, as terminology varies between aircraft manufacturers (but principles are mostly the same for this topic).


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What is the primary means of IFR navigation for private pilots?
I have been doing a lot of reading into IFR navigation, and have been looking at the various instruments and systems that are used.  I am going to exclude GPS here, as I have been focussing on some of the more 'old-school' methods.
My question is, if a private pilot decided to fly their GA aircraft from A to B, lets say a distance of 500nm, what IFR systems would they use to navigate?
My first answer myself would be VOR, but the range seems to be a limiting factor.  For example, high altitude VORs have a maximum range of roughly 130nm (http://flighttraining.aopa.org/magazine/2000/December/200012_Features_The_ABCs_Of_VORs.html).  If we were flying between two major cities, this wouldn't be an issue, as I would expect plenty of stations to track to on the way, but what if I was flying between two airports where the VOR stations were positioned 300nm apart?  Is this sort of IFR navigation only possible with GPS?
Thanks in advance.

There are numerous options, and it depends highly on your route. But there are generally enough VORs scattered across the country such that you should be in range of a couple of them pretty much everywhere. As mentioned in another answer, there are NDBs, but in the continental US, generally, the ones not on an approach are getting fewer, as the FAA has followed a path of not repair them once they break. Other parts of the world, still use them and there are also NDB based airways(AIM has examples for how they can be charted on US charts).
If you had to plan a  flight from a field that doesn't have a navigational fix, and you don't have GPS, you'd start by looking for airways near where you are. Once you find some that go in the general direction you want to go, you start figuring out intersections near that or how you plan to intercept the airway. Then you end up most likely planning a zig-zag course following airways towards your destination.

In the UK I generally use VORs where possible, then NDBs, then good old dead reckoning. GPS spoils the fun!... and besides the planes I regularly hire are at a flight school and each has a different GPS installed (or in one case no GPS at all). You "program" a VOR radio in pretty much the same way in all planes (or at least all of the ones I fly), but I reckon trying to remember what random combination of buttons, twists and presses I need to enter a route on each system is far more likely to end in a mistake.
For example to get from my local field to our nearest GA-friendly airport with an ILS is 2 VORs then an NDB (located at the ILS airport, and forms part of the procedural ILS).
I only use for dead reckoning for short legs, like getting through gaps in airspace around London - e.g. track outbound on from VOR to 8DME, then heading x for 7 minutes, then heading y until you intercept the z track onto an NDB]. I guess if you're in an area with very sparse VOR coverage you probably have less airspace issues, so less need for accuracy (terrain issues notwithstanding - but the higher you are the further the reception). In that case longer-distance dead-reckoning may get you between VORs.
I also have an app on my iphone which warns if I'm about to bust controlled airspace, but that breaches your "no GPS" question :).
Technically you can use "VDF" too in the UK (i.e. some airports can tell you your bearing from radio transmissions), although I've not tried that myself.

How do you file a flightplan for dead reckoning? That sounds counter-intuitive for IFR....

Just out of interest, whats that app called?

@MotherGrinningBird Thanks, it was user incompetence on my part, somehow I created two logins and tried to comment with the other.

@MattKelly It's the Aware app (https://itunes.apple.com/gb/app/airspace-aware/id522037116)

@SentryRaven I don't. I only have the UK "poor man's" IR rating (a.k.a. the IMCr or now IR(R) ) which doesn't allow me in class A. So my IFR flying is mostly done in uncontrolled class G (no flight plan required) or class D (pop-up plan, but usually around an airport so with VORs, NDBs and/or radar vectoring)

@Phil I didn't even know that was possible in EASA land. IFR in class G does not require a flightplan in the UK? Do you possibly have the source in your AIP for that, before I start to dig for it myself?

@SentryRaven It's in UK AIP ENR 1.10 (more precisely, it's implied by omission from para 1.3.1.1).

@Phil Huh... nice little loop hole there...

@SentryRaven no flight plan is required for IFR in Class G in the USA, either. However we have much less Class G here than in the UK (and less every year). For the most part you will only find Class G below 1200' or 700' AGL which is not very conducive to safe IFR (IMC) flight.

You can use Automatic Direction Finder (ADF) along with Non Directional Beacon (NDB).
Of course, VOR/DME, GPS/GNSS and radar (by ATC) can also be used.

Thanks for replying.  I have found ADF to have a very limited range, much more so than VOR.  It seems to be more useful as an aid during an ILS approach, if not as a non precision approach itself.

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What to do with excess fuel before flight?
I've read that it's recommended to store a plane with full fuel tanks to prevent water contamination.  Some small general aviation planes, however, would exceed their maximum gross take off weight with full fuel and just two adult passengers of average weight.  One option, of course, is to fly with less than a full fuel tank.  This seems like it could be a problem if 50 gallons of fuel need to be dumped which cost the pilot $300.  My question is: what does a pilot do with the extra fuel that needs to be discarded before the flight?

You have a few options,
You can burn it off. Laps in the pattern are great for this. Get to the airport before you need to depart and practice some landings. This may cost you in terms of dollars but at least you are not just dumping it.
You can dump it into gas cans if you have them. Every small GA plane i have ever encountered (mostly pipers) has fuel sumps for testing your fuel during your preflight. Most of these sumps can be latched open and you can drain it into a gas can for use later. you should always test for water before doing this. If you rent you should ask the FBO what their policies are on dumping/reusing fuel. I cant find any specific legislation on it but it seems that its common practice (for the airlines at least) to only put the fuel back in the same plane (or within the same fleet) to prevent cross contamination of things that can build up in the tanks.
The sump on the pipers I fly looks like this

(source)
Dont have the plane filled up. If you rent planes like many GA pilots do and you plan to take up 4 friends for an evening sight seeing flight ask the FBO to not fill the tanks if someone is using it before you.
Dont use all the tanks. This will vary plane to plane but some planes have 2 or more fuel tanks which may be independently selectable. You may be able to (weight and balance permitting) keep some of the tanks dry if you know you regularly short hops with big loads.
For the sake of a complete answer I will mention that planes can be flown over gross weight, I don't advocate this nor would I ever attempt it but it does happen here and there, here is a discussion on it if you are curious.

I've never seen those kinds of drains on a Cessna. In my plane I just fill to 44 gallons instead of 50 during the summer, or after a flight when I know I have a heavier load to fly coming up.

'This seems like it could be a problem if 50 gallons of fuel need to be dumped which cost the pilot 300 dollars.'  Yes, especially as many '4-seat' planes only carry 50 or 60 gallons to start with! $6/gallon seems a bit high, I suppose it depends where you are. I believe my home airport is 4.19 USD at the moment.

Given the well-known unreliability of GA planes' fuel gauges, I would never accept a rental plane with less than full tanks. That is the only way to be sure how much fuel you actually have.
Burning off fuel in the pattern or draining it into tanks are IMHO only reasonable options for an extremely short flight or if you're only overweight by a few gallons.
The three most useless things to a pilot are altitude above you, runway behind you and fuel on the ground. Every pound of fuel you don't have onboard means fewer options (or "outs") available if something goes wrong in the air.
Far more likely is that I would simply rent a larger plane (e.g. C182 instead of C172) that could carry the desired load with full fuel. This is obviously an easier decision for renters, but even if I owned a C172, I'd still prefer renting a C182 for one trip over giving up fuel/outs. If I need to do that often enough that the cost or inconvenience mattered, then it's time to trade up to a bigger plane.

No, full tanks are not the only way to know how much fuel you have.  With most light planes (at least in my experience) you have (or make) a measuring stick, and check.  FWIW, with my Cherokee I almost never fill the tanks completely.  At most it's "to the tabs" which is about 40 gallons of the 50 max.  At ~8 GPH, even 40 gallons lasts longer than I care to go between pit stops.  And every extra pound of fuel means less climb performance, which matters when you fly into a lot of short mountain fields.

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What is this tube-like thing protruding from under an A330's wing?
I took a flight for a business travel and I saw something new for me on the wing. I highlighted that part in a red circle in the picture below. The aircraft is an Airbus A330-200.
What is it and its function? I know the anti-shock bodies and static wicks, but what's that?

As a contrast, there isn't such a thing on this other aircraft, an A320, except a static wick.

See also: How is fuel dumped in aircraft?

The item circled on the A320? is a static wick.

It is the port for mid-air fuel jettison.

(Image credit: http://opilotoprofissional.blogspot.hk/2011/08/consideracoes-sobre-overweight-landing.html)
The A330 is a long range airliner, capable of serving flight routes that are 10~12 hours long. It is equipped to dump fuel while in-flight to reduce its landing weight.
The A320 is not a long range airliner, thus there is no need to install such equipment on it.

And some conspiracy theorists say it is a chemtrail sprayer.

@mins To some extent, yes, but not what they say it sprays.

@kevin, Thank for your answer. Yes. The A330 flight is an international flght, while the A320 flight is a domestic flight. Your explanation really makes sense.

Your answer seems to say that dumping fuel before landing is BAU. To clarify: Fuel is never dumped, unless there is an urgent need for. Dumping capability exists only on aircraft that have an authorized mass for taking off larger than for the maximum mass for landing. Decreasing this mass would be done by dumping fuel if time lacks and they need to return to the ground before having burnt the necessary quantity. Still dumping fuel is a very slow operation. New aircraft have often mass limits for T/O and landing that are similar, so they can land without mass excess at any time.

@Huang "short range" isn't always the same as "domestic flight". For example London Heathrow to Paris Charles de Gaulle is only about 215 miles (350 km) but it's an international flight, not domestic.

@alephzero and an ORY FDF one is 6850km but still domestic :p

@Antzi Yep, and JFK-HNL is over 8,000 km and still domestic. There are probably some domestic flight to Guam or other such remote islands that are even longer.

@mins All three of the most recently-designed common long-haul aircraft (A380, 787, and A350) have MTOW far in excess of their max landing weight. Smaller aircraft typically don't need fuel dump capability, but almost all aircraft designed for long-haul operations do, regardless of whether they're new designs or not. It would take a lot of extra weight to make the landing gear on a long-haul aircraft strong enough to certify for landing at MTOW and, since that's not needed in normal operation, they don't design it that way.

@reirab: I don't know where I found this idea which is indeed wrong, thanks for correcting.

The pod as a whole is an aerodynamic fairing for the screw Jack which drives the position of the fowler flaps on the wing.  The pipe as pointed out above is a fuel dump vent to jettison fuel as needed in flight.

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How do turbochargers aid engine performance as density altitude increases?
How do turbochargers improve engine performance at high altitudes / density altitudes?
Could you also address how this benefit could become a liability at low density altitudes, for example when the density altitude is negative?

See my related question, and the good answers there.

John Deakin has a really good series of articles on AvWeb describing aircraft turbochargers: http://www.avweb.com/news/pelican/182102-1.html

An oversimplification for sure: Turbochargers essentially compress the air going into the engine (cylinders) to maintain (near) sea level pressure internally, so the external density altitude doesn't affect the performance of the engine.
The "liability" at low density altutudes is that it is possible to over-boost the engine, potentially damaging it. See the related question for more in-depth explanation and the liability of having a turbocharger at low density altitude.

Also worth noting that - as mentioned in the answers on the other question - normally aspirated engines will produce greater than rated power at negative density altitudes. This factor is generally ignored because it's not as substantial a difference as you see with turbochargers, but it's why I can cruise in the yellow arc at 65% power in my lowly PA28 Cherokee in winter.

@voretaq7: but would that not have the same internal pressures as 75% or more at standard conditions?

@Qantas94Heavy Yup, and around the same equivalent power production - more air to push around everywhere (in the cylinders & around the prop).

Turbochargers increase available engine performance by increasing the amount of fuel/air mixture that can be burned in the cylinders. This is accomplished by compressing the air before fuel is mixed in.
The performance of a reciprocating aircraft engine is directly dependent on how much fuel can be burned and converted into heat energy, which in turn is converted into kinetic energy (motion). The amount of fuel that can be burned is dependent on how much air (actually the oxygen in the air) is available to burn with the fuel. An increase in altitude causes a decrease in air density and therefore less air available to be burned with the fuel. In a non-turbocharged (technically a "normally aspirated") aircraft engine, the reduction in available air will cause a corresponding reduction in available power. A turbocharged engine overcomes this deficiency by compressing the air brought into the engine, thereby increasing the amount of fuel that can be burned with the air, and increasing the amount of power available.

The turbocharger will rotate at a higher RPM at altitude, compressing the air such that the amount of fuel & air entering the combustion chamber is nearly the same as at sea level. From idle to full power will take longer at altitude and it may not be possible to successfully restart such an engine at high altitude until you have descended to an altitude where pressure is more favorable to start the engine.


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Is skin friction drag affected by material?
Normally, friction between surfaces is affected by the materials. Can skin friction be reduced by a low friction material like Teflon?

Can you elaborate on your question? What is the aviation link?

I'm not too sure of your question.  But the answer is yes.  Friction and drag are almost completely dependent on material.  For example, a rocket with "perfectly" smooth paint will use less fuel than a rocket with a normal matte finish.

Indirectly, yes. Friction goes up when dirt and smashed bugs accumulate on the wing. A low surface energy coating might well reduce their stickiness, so the wing collects less dirt and has less roughness. This is especially helpful when it helps to delay the transition from laminar to turbulent flow.
Another way to delay that transition would be a soft surface which could help to dampen the characteristic Tollmien-Schlichting oscillations from which the transition of boundary layer flow from laminar to turbulent springs. Accelerated flow is naturally damped (the amplitude decreases relatively to flow speed), so it stays laminar on a smooth wing. Once the damping turns negative (i.e. the oscillation is increasing), the turbulent transition is imminent. When the wing is not only smooth, but also soft and helps to dampen those Tollmien–Schlichting oscillations, even unaccelerated flow might stay laminar for longer, which again reduces friction drag. So far, I am unaware that this effect has been exploited successfully on an aircraft, though.
The friction between gaseous substances and solids is not affected by the surface energy of the solid, so a direct reduction in viscous drag due to a polytetrafluoroethylene coating will not happen.
I trust you know how drag depends on surface roughness. If not, please feel free to post another question.

According to this paper some kind of roughness can lower skin friction.
The idea is to create small "barrels" of gas that rolls between surface and the gas flow. The surface has ridges perpendicular to the flow direction. They guide air in small rotating air tubes.
Shark skin also has a reduced skin friction. Here is how it looks :

I think it provide both advantages of ridges (gap between scales) and the soft surface properties Peter is talking about.


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Is the Falling Leaf maneuver used for UAV recovery?
The Falling Leaf maneuver is a way to lose altitude by descending like a tree leaf. Is this maneuver used in the recovery of UAVs?

Source.

The maneuver as described is not a particularly efficient way of losing altitude: You're alternately stalling & recovering from the stall.
More efficient descent procedures exist.
The technique of holding the aircraft in a wings-level stall (or putting it into a spin) was used in the early days of aviation to get back below a cloud deck if you were trapped "on top": when you broke out below the clouds you would recover from the maneuver & proceed to your destination / landing (if you were lucky enough to have sufficient altitude to recover when you came out of the bottom of the clouds).
Needless to say neither of these maneuvers makes much sense for an unmanned aircraft: If your goal is a rapid descent you will execute a maneuver that gives you the best possible descent rate (such as the emergency descent procedure in the POH, or the one in the Airplane Flying Handbook); If your goal is to get back below the clouds you've already busted the regs (you need to maintain visual line-of-sight with your UAS), but if and when the regulations change you should also be able to recover using more modern techniques (like descending on an instrument approach or using a synthetic vision system) to ensure you don't hit anything, like another aircraft.

Tnx
In fact, I want to use this maneuver(falling leaf) for UAV recovery(landing) and not just for loose altitude
is falling leaf efficient way for this act?

@P.azarakhsh Landing involves more than simply stalling the aircraft until it hits the ground. Descent rates in the "falling leaf" maneuver can be upwards of 200ft/minute depending on the aircraft, and when you hit the ground at such a rate of descent we generally call it "crashing" as opposed to "landing". You would probably be better off using a parachute recovery system if you're not confident in your ability to land in the usual way.

Actually, my curse project that how landing a uav with falling leaf ro flat spin maneuver. with out  parachute recovery system. which one is better for this act? (said the RQ-170 recovery landing for this way in Iran 4 years ago)

@P.azarakhsh: In RC aerobatic flying there is a maneuver called the "elevator" or "parachute". Search "elevator maneuver" on youtube. I often use it to land my hand-launched planes at sites without large fields or landing strips. You need a fairly low wing loading though for it to be useful for landings instead of just for show. Otherwise you'd come down too fast and damage your plane.

I use falling leaf with my suas when I want to loose altitude quickly, and don't want to risk entering vortex ring state.  For me, I can drop from 350ft to 30 ft reasonably quickly, and feel that I have full control using line of site. After reaching about 30ft, I can easily pull out of falling leaf and do a nice slow landing.

While not a "Falling Leaf" Maneuver, a "Deep Stall" to landing is actually a very common way to recover a UAS. This is the default behavior for RQ-11 and RQ-20. The systems are designed for this and absorb the energy of the fall in padding and by breaking apart.  Each system has a spares kits for wing panels and nylon fastners. An advantage of this method is that it improves accuracy by simplifying energy management; just fly over the intended recovery zone and stall it in. The vehicle will be close to where you wanted to land.


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Flight Level Change or Vertical Speed - When to use it?
I've heard that some pilots have this difficulty to determine the correct use of both features. So, which is the difference between using the vertical speed, instead using the flight level change during a descent? When, and how to use it?

FLC mode maintains airspeed during a climb or descent, while VS mode maintains a specific vertical speed.
Often air traffic controllers will request that you "maintain 250 knots in the descent" or something to that effect, which is much easier to achieve when using Flight Level Change. As another answer points out, by maintaining airspeed, climbs are made safer as the autopilot will not attempt to maintain a rate of climb regardless of whether or not the airspeed is safe.
FLC mode is typically only available in advanced autopilots, and as far as I know they need to connect to an Air Data Computer to get the necessary information.
How to use FLC would depend on the equipment available to you:

aircraft with auto throttle will maintain speed and an appropriate rate of descent automatically.
for aircraft without auto throttle you'd set your target altitude, enable FLC, adjust your target speed if needed, and set your throttle for climb or descent to maintain the desired altitude change rate.

I'm referencing the Garmin GFC700 as it's the only autopilot I've used with FLC mode, but I imagine the same steps and rules would apply.

Just MHO:
Vertical speed should never be used when climbing because you could stall if insufficient power is added for the requested climb rate. Using FLC when climbing guarantees you maintain the best airspeed (best rate or best angle, depending on the situation)
On the other hand, when descending I always use VS mode because it gets you down to the proper altitude in time (if you've calculated the required VS before starting your descent). It also prevents physical discomfort for you and your passengers. If you use FLC during the descent you have to be very careful with power in order not to exceed safe airspeeds (in addition to the discomfort caused by excessive descent rates)
Not an expert opinion but just a personal opinion...

This is a good point and one I failed to mention in my response. Because FLC is essentially airspeed-hold mode, there's a much bigger margin of error. :)

We used vertical speed hold in the climb routinely in the EMB-145 because airspeed hold would porpoise worse than a student pilot while it chased the speed bug.  As long as you are doing your job and monitoring the airplane, you are in no danger of stalling (and add to that we climbed at 290 kts transitioning to M.65 or M.60 so we had a decent stall margin).

V/S "never" used while climbing???  If I'm climbing to FL300 and traffic ahead is descending to FL310, I absolutely would use V/S in order to shallow out the climb and avoid a TCAS RA!  USUALLY level change (or VNAV -- accomplishing the same thing) is the best option for climbing, but not always.

@RalphJ Note that I ended my answer with "just a personal opinion"

@RalphJ you can still shallow out the climb while in FLC mode though. In some autopilots it's even done using the very same up/down buttons that you would use when you are in VS mode (e.g. GFC 700).

They are different modes that control aircraft pitch in different ways, and as a pilot you select what you want based on your current requirements.  Note that the modes even behave differently depending on the aircraft / autopilot, so referring to the actual aircraft/autopilot documentation is essential.
Many autopilots don't even have a Flight Level Change mode, but instead have an Indicated Airspeed (IAS) mode.
Autopilot modes like these are typically "dumb" and just do what they are told, without taking anything else into consideration.
Regardless of which mode that is used, remember that it is the pilot responsibility to monitor the aircraft and to make sure that it is doing what they want it to do!
Indicated Airspeed / Flight Level Change

This mode usually adjusts the pitch of the aircraft in order to maintain a specific airspeed.  In simple systems, the only inputs that are used are airspeed and aircraft pitch.
You usually control the vertical speed of the aircraft by making power adjustments:

By reducing power, your vertical speed will decrease.
By increasing power, your vertical speed will increase.

In some systems your actual altitude is compared to the selected target altitude and a minimum climb or descent is maintained even if the airspeed can't be maintained.
In some systems the aircraft altitude is used to change the behavior (for instance, in one aircraft that I have flown, if you are below 8,000 ft MSL and hit FLC, it will descend at 1,000 FPM but if you are above 8,000 feet it specifies a 250 KT IAS hold).
In some systems, the pitch is adjusted to maintain a specific climb/descent schedule which automatically changes based on altitude.  For instance, a descent schedule might be Mach 0.80 until 29,000 ft., 350 KIAS until 10,000 ft. and 250 KIAS below 10,000 ft.
Another aircraft that I have flown in the past even had two climb schedules. You could toggle between the "normal" climb and the "high speed" climb by hitting the FLC button more than once.
A lot of autopilots (especially older ones) tend to oscillate around the target airspeed and constantly pitch up and down while trying to fly a specific airspeed.  For this reason (keeping in mind that passenger comfort could be an issue) many people avoid speed modes, especially at higher altitudes.

Vertical Speed

This mode usually adjusts the pitch of the aircraft in order to maintain a specific vertical speed.  Again, it is usually a "dumb" mode and doesn't look at anything but vertical speed and aircraft pitch.

Flight level change in the advanced systems like Airbus  is coupled to autothrust and selects Climb (CLB) or Idle thrust as appropriate.

@JanHudec While true, autothrust is an independent system which just responds to other factors based on the mode that it is set to and whether or not they are even engaged.

@Lnafziger: I am pretty sure in Airbus if A/T is engaged and A/P is in "open descent" (flight level change to lower), idle thrust is selected (and A/P maintains the selected speed with pitch). It's described in this incident report.

@JanHudec I have no doubt that it works that way, but like you said, if auto throttles are engaged.  It's a different system than what the question is about so I didn't discuss it here.  :)

@Lnafziger: Yes, A/T has to be engaged. The reason for that incident was that pilot selected idle manually, which did not change the rate of descent, but disengaged A/T, so the thrust was not automatically increased again when they reached the assigned altitude.

In "full up" FMC/VNAV/Autothrottle airplanes, Level Change tends to be an "all or nothing" option for power: full climb power to go up, and flight idle to come down (with pitch holding the commanded speed in both cases).  With Vertical Speed, the pitch holds your climb rate constant, and the throttles vary to hold your airspeed.  With a sufficiently large V/S value commanded, you reach either full climb thrust or flight idle, and then the throttle can't affect airspeed any more -- so you can lose airspeed with a steep climb commanded, or gain it with a steep descent.
And then at some point, you look up & wonder why we're so fast/slow, and realize that V/S has done you in, and you go back to flying the airplane.  :)
One reason that I personally prefer V/S over level change in certain circumstances is that the latter tends to be fairly aggressive about maintaining speed, so in gusty conditions the autopilot (in level change) will end up pushing & pulling quite a bit to hold the speed +/- a knot or two.  I think that tends to be an uncomfortable ride, so I'll go to V/S and let the speed fluctuate (the autothrottles can chase it, or I deselect them & just leave a stable power setting) while the pitch attitude stays constant.
At some point, you go back to a speed mode (i.e. once you level off), but for the stable pitch instead of constant push/pull/push/pull, V/S has its advantages.  Just don't ignore it long enough to let your speed do undesirable things to you!


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Is it legal to overload a plane in Alaska?
Is it true that it's legal to fly a plane over max gross weight in Alaska? If so, what are the rules?

You should probably contact the local FSDO and inquire about obtaining a ferry permit to conduct a flight that is overweight. Their inspectors can advise you about such weight and the flight limitations on airworthiness.

Under some conditions, FAR §91.323 allows for a 15% increase (up to 12,500 lbs) in max gross weight in Alaska:

(a) Notwithstanding any other provision of the Federal Aviation Regulations, the Administrator will approve, as provided in this section, an increase in the maximum certificated weight of an airplane type certificated under Aeronautics Bulletin No. 7–A of the U.S. Department of Commerce dated January 1, 1931, as amended, or under § 91.325 14 CFR Ch. I (1–1–05 Edition) the normal category of part 4a of the former Civil Air Regulations (14 CFR part 4a, 1964 ed.) if that airplane is operated in the State of Alaska by—

A certificate holder conducting operations under part 121 or part 135 of this chapter; or
The U.S. Department of Interior in conducting its game and fish law enforcement activities or its management, fire detection, and fire suppression activities concerning public lands.

(b) The maximum certificated weight approved under this section may not exceed—

12,500 pounds;
115 percent of the maximum weight listed in the FAA aircraft specifications;
The weight at which the airplane meets the positive maneuvering load factor requirement for the normal category specified in § 23.337 of this chapter; or
The weight at which the airplane meets the climb performance requirements under which it was type certificated.

(c) In determining the maximum certificated weight, the Administrator considers the structural soundness of the airplane and the terrain to be traversed.
(d) The maximum certificated weight determined under this section is added to the airplane's operation limitations and is identified as the maximum weight authorized for operations within the State of Alaska.

One possible reason for this is that Alaska Statute Section 02.35.110 requires aircraft operating to/from and within Alaska to carry additional emergency and survival equipment:

(a) An airman may not make a flight inside the state with an aircraft unless emergency equipment is carried as follows:

the following minimum equipment must be carried during the summer months:

rations for each occupant sufficient to sustain life for one week;
one axe or hatchet;
one first aid kit;
an assortment of tackle such as hooks, flies, lines, and sinkers;
one knife;
fire starter;
one mosquito headnet for each occupant;
two small signaling devices such as colored smoke bombs, railroad fuses, or Very pistol shells, in sealed metal containers.

in addition to the equipment required under (1) of this subsection, the following must be carried as minimum equipment from October 15 to April 1 of each year:

one pair of snowshoes;
one sleeping bag;
one wool blanket or equivalent for each occupant over four.

(b) However, operators of multi-engine aircraft licensed to carry more than 15 passengers need carry only the food, mosquito nets, and signalling equipment at all times other than the period from October 15 to April 1 of each year, when two sleeping bags, and one blanket for every two passengers shall also be carried. All of the above requirements as to emergency rations and equipment are considered to be minimum requirements which are to remain in full force and effect, except as further safety measures may be from time to time imposed by the department.

Note that newer aircraft are not necessarily eligible -- only primary category aircraft that is certified under the old CARs and aircraft certified under the very old Aeronautics Bulletin 7A (superseded Nov 1937).

@Qantas94Heavy I read a post where somebody said that only pre-'45 aircraft were eligible, but I couldn't find a reliable source for it.

I took a look at that too, but I don't understand the reasoning behind it, nor could I find any authoritative sources. Once a aircraft is certified, it's still certified under that even if built much later, right?


text:
What are the properties of a good general aviation training aircraft?
I've been told that the best kinds of planes to train in are very small ones, like Cessna 150s and 152s.  But I've never been clear as to why.  I know they are cheaper to operate, so is operation cost the only thing?  Or are there aerodynamic properties that 152s have that make them "easier"?  What makes for a good training aircraft?

a second set of controls so the trainer can take over in a pinch?

Don't all aircraft have that though?  It does make we want to train in an F-16D, for sure...

I probably should tag this GA, as that's really the kind of answer I'm looking for...

@JayCarr Not all GA aircraft have dual controls. Most do, but not all. And some have "throw over" controls that look like this. These can't be used for pre-PPL training per 14 CFR 91.109(a)(2).

@frederico, sure, but it's likely considered an "advanced trainer". Jay is asking about primary trainers, from what I can tell.

Cost is certainly a primary factor in choosing smaller planes. It makes training much more accessible to people with less money to spend.
Small planes are also easier to fly for various reasons. They fly slower and respond more quickly than large aircraft, which gives the pilot much more margin for learning. Being more maneuverable can help them escape tricky situations.
These planes are also generally designed to be resistant to and recoverable from common aerodynamic disasters like stalls and spins. See this related question for more information. There are FAA requirements for single-engine planes in FAR 23.221.
Smaller planes generally also have fewer and less complex systems, which makes the necessary training easier to complete.
They can also operate from smaller airports, which gives a student more choices of where to do their training.
Of course, there are always exceptions to these qualities, and large planes can have similar ones, but they hold true in general.

All good points, +1. I'd just add that cost, which the OP mentioned, is also a huge factor. Why pay $200/hr or more for a larger complex airplane when you can learn the same basic skills paying $100/hr or less? :)

Indeed. The prop revolves around its axis, everything behind that revolves around money.

@dvnrrs Right, but I'd like to steer clear of cost, that seems more a matter of personal finance.  All I'm really wondering about is what the best physical/flight characteristics of a training should be, without really considering cost.

@JayCarr When talking about flight training cost is the 800lb gorilla riding the white elephant into the ballroom...

@voretaq7 - lol, and I acknowledge that, but I'm not asking about the Gorilla or the white Elephant, I'm merely asking about the ballroom floor.

@JayCarr Gorillas and Elephants are not usually potty-trained/housebroken. You might not want to go in the ballroom for a while :)

You people are hysterical....@fooot Could you possible expand on how they are made to be resistant to stalls and spins?  Wing design?  Balance consideratins?  I'm looking for a few more specifics.  I'll mark this as the answer if I could just get those details...

@fooot Hmm, maybe you've got a point.  I could just ask that as another question.  Then you could just answer that one and reference it here ;).

@JayCarr Interestingly designing aircraft to be easier to spin was, at one point, a desirable characteristic for a trainer. See for example the PA-38 Tomahawk.

@voretaq7 - lol, that article makes it sound like they made it just a tad too easy to spin...  But I get your point.  You want a plane that will stall/spin, but will be predictable when recovered.  Thus you can practice recovering from those situations.

The Cessna 150/152 is considered a good trainer aircraft for a combination of desirable qualities:

Low cost - An older 150 airframe is comparable in price to a car (between \$25k and \$50k usually depending on internal instrumentation), making the loan payments a little easier than that Gulfstream.
Mechanical simplicity - One engine with fixed-pitch prop, fixed landing gear, cable control linkages, manual everything. This gives three main advantages:

Less to break. When things break on an airplane, you can't just pull off to the side of the road and call a tow truck. So, the simpler the system, the less that can go wrong.
Less to have to learn. More complex aircraft increase the pilot's workload for standard procedures such as approach and landing (and variations like the missed approach/go-around). Retractable gear and variable prop pitch, plus flaps, define a "complex" aircraft in FAA regs requiring a special endorsement.
Less to inspect and maintain. Preparing to fly an aircraft always incorporates a preflight "360" walk around the aircraft checking control surfaces, intakes and engine compartments, lights, external components of instruments like the pitot tube and stall horn, etc, followed by an internal check of systems like the radios, control linkages, flight instrument displays etc. This takes more time the more systems you have on board to check. Those same systems also have to be inspected more thoroughly for the annual mechanical certification (a more in-depth counterpart to a car's safety inspection) which will increase the "total ownership cost" of a more complex airframe.

Docile handling - The 150 is nicknamed the "Land-o-matic" for its reputation for being an extremely forgiving, easy-to-fly aircraft. Cessnas in general tend to handle very well for "everyday" flying because of their high-wing design; this generally makes them less susceptible to entering fatal upsets like the spiral dive (they can still spin-stall on you).
Full instrumentation available - If you want your instrument rating, you need access to a plane that will allow you to practice IFR, and that includes the full set of IFR navigation instruments. The 150/152's instrument panel, while small and simple (like the rest of the aircraft), is fully decked out for radionavigation, and a GPS unit is typically pretty simple to add.


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How old is too old to become a pilot?
What is the highest age at which you can decide to become a pilot for a major airline, a pilot for a cargo airline, or a private pilot?
I'd like to know for Canada or France mainly. But I wonder whether these countries will have rules that are too different from the US and EU.

First up, commercial pilots (both major airlines and cargo airlines): It depends on the country and airline, but the retirement age for a pilot is generally 65 in most countries, and almost always somewhere between 55 (e.g. British Airways) and 65 (standard in much of the U.S.)
There is no set last age at which you could be recruited, so in theory it's just before those ages, but in practice you're unlikely to be hired by a company if you can't work there for at least 5 years.
If you're not yet a qualified pilot, though, you'd have to account for this time too (no company is going to hire you and train you just in time to retire). In practice, therefore, the likely realistic age is at least 10 years prior to the retirement age for the country/company in question, and likely 15.
And if we move into pure conjecture for a moment, I'd hazard that you'd find it quite hard to find a company willing to take on an untrained pilot much after their early-mid 40s.
As for a private pilot: As long as you can pass the medical you can fly and, indeed, learn to fly, at any age. There's no maximum age, although as you'd expect most (but certainly not all) people start to struggle with passing the medical sometime in their 70s. By 80, there aren't too many pilots still flying around.

The question also asks for private pilots, for which I don't believe there is a maximum age anywhere in the world as long as you can pass the medical. And just as an extra point, in Australia (and I think New Zealand) there is no mandatory retirement age for pilots.

Good point re private pilots, although in Aus and NZ I believe most if not all companies define their own retirement age.

Concerning private pilots: I earned my PP-Glider rating with a man who first flew gliders over Europe...in the early 1940s.  He was 85 or 86, I think, when he got the rating (taking an extra year or two compared to other students in our year who were in their teens).  However, as he got older, he also made sure to never fly without someone else in the backseat.  It's possible, especially for gliders in the US (self-certifying medical), but requires prudence.

If he flew gliders over Europe in the early 1940s, I sure as hell don't want to be the person asking him to hand me his license

@JonStory Not all of Europe was actively engaged in WWII, if that's what you had in mind when writing the above comment.

Well it was a joke, but also there were only a handful of European countries not involved in WW2, representing less than 5% of the European population at the time. Odds are that they were flying their glider as part of the war effort, or in preparation for their country being caught up in it.


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How does Boeing park several airplanes on a single runway at Paine Field?
On DigitalGlobe, I saw the following picture in an article, which talks about some of the best aerial shots of 2014.

Paine Field, Washington
Questions
1) Did the plane, highlighted with a yellow circle, need to reverse to line up so neatly even though it just turned (I assume). Is the turning radius really that small that it takes very little space for a big plane to change direction so quickly on ground?
2) Is there any special reason that all the planes are on one side of the runway and not centered on the markers? They all seem to be lined up towards the left side of the picture.
3) Isn't that too close when there is another plane parked so close in proximity? Provided there is ample space available.
4) Is it just that the scale of this picture, taken from a satellite, making them look closer than they really are?
5) What does that Double marking 7/91 Mean on the North East end of the small runway? usually that is a single number indicating the heading. That can't be 91, then what does that 91 mean?
6) Why are  there a bunch of planes that are about stacked on top of each other towards the bottom right of the photo, on the ramp to 29?
P.S: I know they are parked and are not taking positions to take-off.

7) Is there really a plane without wings? Yes, there is.

Yep for sure there is :)

Very carefully would be my answer. ;-)

The Cessna landing on the runway 34L is probably so confused by all those huge planes... If the pilot's not familiar with the airport.

Most of your questions seem to be answered by the current answers/comments, but since you are wanting more detail...
1) Did the plane, highlighted with a yellow circle, need to reverse to line up so neatly even though it just turned (I assume). Is the turning radius really that small that it takes very little space for a big plane to change direction so quickly on ground?
Yes, either the plane in the yellow circle or the one directly behind it had to be reversed into its spot. When airplanes are being repositioned around an airport, they are typically towed, because it requires less fuel and it's easier to start up a tug and hook it up than to power up a large jet for taxi. The tug is also able to push the jet backwards when needed (which also happens routinely when the jet departs from an airport gate).
Runway 11/29 at KPAE (currently closed except for taxiing for obvious reasons) has a width of 75ft (23m). According to Boeing, a 787-8 (the indicated plane and all but the green 747 at the northwest end) needs 128ft (38.9m) width to make a turn. This assumes a steering angle of 70 degrees, with the R2 outer gear at one edge at the beginning of the turn at a radius of 46ft and R3 nose gear at the opposite edge halfway through turn at a radius of 82ft. So it would not be possible for a 787 to turn around on that runway. Certainly not a 747. Even if they tried to do something like a three point turn, the distance between the nose and main gear is 74ft 9in center to center, which puts the wheel distance just over the runway width.
2) Is there any special reason that all the planes are on one side of the runway and not centered on the markers? They all seem to be lined up towards the left side of the picture.
They are probably on the south side to provide as much clearance as possible for taxiway D immediately to the north (as Lnafziger commented). The taxiway to the south is marked as closed (might be W?). The Additional Remarks on AirNav include (with my comments):

...TAXIWAY D BETWEEN D2 AND ALPHA (north section of D) RESTRICTED TO WINGSPAN OF 118' OR LESS. TAXIWAY D BETWEEN D2 AND GOLF (south section of D) RESTRICTED TO WINGSPAN OF 49' OR LESS.
TAXIWAY W CLOSED INDEFINITELY (probably south of runway 11/29).
TAXIWAY INTERSECTIONS D2, D3, AND D4 CLOSED INDEFINITELY (between runway 11/29 and taxiway D to the north).

For reference, the 787-8 has a wingspan of 197ft 3in (60.12m).
3) Isn't that too close when there is another plane parked so close in proximity? Provided there is ample space available.
While crew must certainly take care to avoid collisions, planes can be parked very closely together if needed. See your question 6 for an example (also boneyards or aircraft carrier hangars). Since the planes will also be towed out of their positions, jet blast should not be a concern.
Although there is more space at KPAE than on an aircraft carrier and fewer planes than at a boneyard, there were still issues of space with so many planes on the ground. There were issues with production and engine availability as slookabill mentioned, as well as the grounding due to the battery issues.
4) Is it just that the scale of this picture, taken from a satellite, making them look closer than they really are?
The picture seems to be taken from close to directly overhead, so the apparent distance is probably fairly representative. Here's another view for comparison.
5) What does that Double marking 7/91 Mean on the North East end of the small runway? usually that is a single number indicating the heading. That can't be 91, then what does that 91 mean?
As ratchetfreak mentioned, the marking is at the north end of the runway, so it is meant to be viewed facing south as 16L.
6) Why are there a bunch of planes that are about stacked on top of each other towards the bottom right of the photo, on the ramp to 29?
Similar to the reasons explained for the other questions, the planes are parked for some period of time. The ground crews want the planes to take up as little area as possible. These appear to be 737's and are probably parked either for maintenance or for reasons similar to the 787 (production).

I notice that the two aircraft in question don't have engines in satellite images currently shown in Google Maps - so I expect they must have been moved into position by tug, assuming engines are only removed inside hangars.

I fly out of KPAE, and the aircraft are parked very close together, especially the 737s in the SE corner of that photo. The 787s are around 30-40 feet nose-to-tail.

@egid thanks for sharing your first hand experience. That must be a nice sight specially coming in for a landing. Any special reason you only fly out of there and not fly in?

Oh, hah, I'm based at PAE. "Fly out of" just means most of my flights start there, really.

It was tugged to that position via tug.
Angle of photo + possibly trying to offset weight, from centerline.
These planes are just being stored there. They'll be tugged to another location
before they even bother to start them up, and I believe most don't
have engines on at present.
They are quite close together.
(from @ratchetfreak's answer:) Turn the image around as if you are coming to land; it's actually 16L a perfectly normal runway number.
Its just a very compact way of parking aircraft in minimum space. Compare the space taken up by those 4 planes versus any 4 nose-to-tail on the runway.

These aircraft are mostly 787s that are the early teen aircraft that were rejected by the original airlines they were slated for, due to so many out of tolerance issues/rework required. They are just being stored on the runway until Boeing can get them into mod/rework status and get them to spec to be able to sell. Right now the mod line seems to be working on one of these aircraft, at a time, and each one taking many, many months to get fully reworked.

I would think that they are keeping the aircraft to the South side of the runway so that they don't interfere with the parallel taxiway on the North side.  I have no idea why weight would be a factor with which side of the taxiway that they are parked on....

@Lnafziger isnt it perfectly normal for an aircraft to be on taxi way and another taking off from the runway? How can they be any interference?

@vasin1987 look at the wingspan you can't expect 2 of those planes to be able to cross each other that central runway looks to be fit for smaller planes only.

Every taxiway and runway has designed safety areas, of limits of their wingspans they can take. Depending on wing span, they could conflict with each other if something isn't taken into account.

In response to your answer to 6) Is it used only there or is that a common practice?

@Iceman Most light GA ramps are interleaved that way to pack more aircraft on the ramp (in fact you can see it in this photo north of the planes parked on the runway too), so it's fairly common for light aircraft. No reason I can think of why it wouldn't be normal practice for large transports. these planes are packed a bit more tightly, but presumably they're not there for long-term storage.

Thanks @voretaq7 for your comment and thanks slookabill for a nice answer!

turn the image around as if you are coming to land; it's actually 16L a perfectly normal runway number.

That was sooooooo obvious, feel even more dumb :) lol

With all due respect, I upvoted your answer, and also merged it into the one above, so that when its "accepted," one answer will be complete. @Iceman might want to consider accepting the other answer

I am sure all those big twins were towed to their parking position on the inactive runway 11/29, and will be towed back to the factory area when the time comes.


text:
How much radiation is an airline pilot exposed to in a year?
Flying exposes us to more radiation since we are closer to the sun, and there is less atmosphere to protect us.
Consider an airline pilot flying on a routine and frequent basis. How much radiation is absorbed per flight hour, and per year?

The difference in distance to the Sun is a tiny fraction of the difference caused by the Earth's orbit and is not a factor.  Only the thickness of the atmosphere is.

As noted by others, distance to the sun is not relevant (other than how it affects solar irradiance).  Your height above the ground is what determines how much atmosphere is above/below you.  At typical cruise altitudes around 50-75% of atmospheric mass is below you.

The Earth's orbit is elliptical, so the distance to the sun varies by about 5 million miles. This is much much much much more than the difference between sea level and cruising altitude.

@RedGrittyBrick Specifically, it's about a million times larger. :) Also, depending on time of day and location, you might actually be farther from the sun than the ground beneath you (though, again, by a completely inconsequential amount.)

Not only the atmosphere, but to a big degree it is about the magnetic field. The deflection of alpha and beta radiation is subject to the field, as they are charged. The shiedling effect of the atmosphere is imortant too of course, but I don't know the numbers.

The average additional annual dose for flight crew is 2.19 mSv (milli sieverts).  http://www.hps.org/publicinformation/ate/faqs/commercialflights.html
The typical annual dose from background sources is 4 mSv (this varies enormously on the Earth's surface). However, as a rough order of thumb, the annual radiation dose of a flight crew member increases by about 50% compared to sitting on the ground.
For comparison with other sources, having a chest CT scan provides you with a 7 mSv dose over the period of a few minutes.
The maximum permitted dose in one year for a radiation worker under US Federal Law is 50 mSv.
For more comparisons of radiation dose, see https://xkcd.com/radiation/
On a technical point, the premise of your question is incorrect.
Flying exposes us to additional cosmic background radiation because we are at a greater height above the Earth's surface, not because we are closer to the sun. We are protected from cosmic radiation by the presence of the Earth's magnetic field, which extends far into space and is not an issue here except very close to the poles; and more importantly, by the layer of atmosphere above our heads that tends to absorb cosmic rays before they reach the surface. At 40,000 feet, the bulk of the atmosphere by mass is below you.
It is not presently believed that a substantial fraction of these rays are emitted by the sun. For one, you will continue to be irradiated by them at night.
(For interest, if you could see the cosmic background radiation, it would be approximately as bright on the night sky as star light is; for complex reasons the two energies are in rough equipartition.)

I was going to reference the xkcd chart but you beat me to it. Great answer!

I'd say radiation from a chest X-ray is 0.013 mSv. Background radiation is said 2-3 mSv per year. If you live in a place with granitic soil, you get around 2.5 mSv a year. Individuals exposed to 6 mSv a year or more should be monitored. Work Exposure is restricted to 20 mSv annually for a period of 5 years, with a maximum of 50 mSv in any one year. An abdominal CT means 10 mSv, so, background average radiation an US person receives a year is considered to have doubled, and this means a very small, but mensurable increase in the risk for Leukemia and Lymphoma (e.g. INWORKS study, K Leuraud et al). Some elements used in construction released radioactive gases as Radon. Radon was found in too high concentrations inside some rooms in certain houses. High Radon concentration exist in Uranium mines, however, the type of radiation matters, and also the pace of radiation exposure.
Extremely energetic Cosmic rays are blocked by atmosphere, but not by an airplane's hull. Also UV radiation is higher in the heights. This induces that flight crews do have a higher incidence of all types of skin cancer, including malignant Melanoma, and also male crew members do tend having more girls than boys in their offspring.
Perhaps the reason for this shift in sex ratio is that the redundant X chromosome in girls compensates for the damages that the other X chromosome may suffer. Boys have only one X chromosome. If other chromosomes from the male parent are damaged, it may result in a higher incidence of miscarriages, even unnoticed ones, in the pregnancies resulting from males working in airplane crews.
Data about Radiation and UV Light as a carcinogen can be found at several cancer organizations sites, as the American Cancer Society, specially in their publication: 'CA, a cancer journal for clinicians', that is of open access. (eg Linet et al, 2012; Kim 2009; Hunter 2005; Heath 1996; Weinstein 1982; Joanna F Haas, 1979; Ryser 1974; Simpson 1958)


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Is a rotary wing craft capable of supersonic flight?
Just what the title states.
Since the Wright brothers, aviation technology for fixed-wing craft has advanced by an order or more. Rotary wing craft on the other hand (I know little about aviation; please correct me!) have advanced significantly by way of lift capacity, and maneuverability. Yet velocity has achieved nothing like the kind of advance seen in case of fixed-wing craft.

Is a rotary wing craft capable of supersonic flight?
How is it limited by contemporary technology?

Though nowhere near supersonic the Sikorsky X2 is worth a read if you've not seen it already, and seems to be about the best in terms of forward progress at the moment.

Anything can go supersonic if you don't need to use it twice.

Currently there is no rotary wing craft capable of supersonic flight.
Combined with the forward motion through the air, the rotating blades attack the air on one side and retreat backwards on the other.  As the aircraft moves faster this poses 2 problems:

The retreating blade has a point of zero air speed, starting from the axis at hover and moving to the tip with forward speed, an effect known as P-factor.  Eventually a large portion of the blade has negative airflow (backwards to what it had when hovering) causing loss of lift control on that side (there may still be lift, but the pitch of the blade has little influence). The craft will roll (and I believe gyro forces will bring the pitch up, and the craft will recover)
The advancing blade will go supersonic, starting from the tip. Aerodynamics change.

There are ideas of new blade actuators that can change the blade for 1) reverse airspeed and 2) supersonic aerodynamics.  As you have noticed, nothing has panned out so far...

For further research the terms dissymmetry of lift and retreating blade stall should help.

The Republic XF-84H "Thunderscreech" was a USAF jet fighter modified with a turboshaft engine and a propeller designed to operate at supersonic blade speeds. It first flew in 1955, and the result was a noise that was literally deafening. During ground engine runs, "the prototypes could reportedly be heard 25 miles (40 km) away."
Whereas there may be some advantages of a supersonic propeller, the side effects (the noise) prohibit the use of a supersonic propeller even for military applications, let alone civilian ones.
The question proposes a helicopter with supersonic blades, at least on the blade advancing side of the helicopter.  There is no research that I know of that would indicate a supersonic blade on the main rotor of a helicopter will act differently than the supersonic blade on a propeller on an airplane.  The assumption is therefore that the blades would experience a very significant increase in drag, and would also produce a very significant amount of noise.

Since the question seems about aircraft theory, I'll answer with theory. The short answer is that anything can, and will fly given enough time and effort.
One of the biggest limitations for making a conventional configuration rotary aircraft fly at supersonic speeds is materials. When a rotary blade is inline with the path of travel, it has to withstand significant compression forces along its long axis from the shock. There are three solutions for a conventional configuration - bigger & stronger blade (heavier) new materials, or shorter blades (less lift).
If you don't mind deviating from conventional design, then introducing a shroud around the blades will allow you to remove these forces from consideration by allowing your shroud to absorb the forces of the created shock. You could probably reduce the weight of each individual blade by bracing it against the shroud, (think - beam braced at one end vs both ends) Since the air between a shock wave and expansion waves is sub-sonic. If you're lucky, and physics doesn't hate you, then you may get expansion waves behind the shroud, so your rotor blades will be in a sub-sonic medium. By pumping air from above the shrouded rotor to the underside, you cause lower pressure on top, higher pressure on the bottom, causing a pressure gradient and generating lift.
This is all speculation based on my limited aerodynamics knowledge. In real life physics usually hates you, and you'll get some really messed up expansion waves and shock waves along the inside of the shroud, coupled with some fugly shocks being formed by the rotor blades themselves. Since prototyping has become super expensive, and wind tunnels seem to be a dying race nowadays, this would have to be simulated with CFD, and as far as I know, CFD isn't that fast and accurate yet, which could explain why this hasn't been tried yet.

A rotor on an aircraft/rotorcraft is basically an airfoil section twisted along its length. This twist is also known as the pitch, and in most cases it is variable. On approaching Mach 1 or the speed of sound, shock waves begin to form on an aircraft (eg. on the wings)  and there is a sharp rise in drag (known as wave drag). This is due to the fact that at high speeds, the airflow can no longer be treated as incompressible flow. The rotors face the same compressibility effects that an aircraft wing  faces near the speed of sound, hence it isn't able to overcome this drag.


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What kind of filters are being used to filter the bleed air?
Bleed air is using by airplanes for various purposes including deicing and also to feed air conditioning units that maintain temperature inside cabin. What kind of filters does bleed air pass through before reaching the cabin?

Although typical HEPA filters are what's used (speaking from Boeing experience only), it's important to understand how bleed air is used in a typical aircraft environmental control system (ECS). Bleed air is taken from the compressor section of the engine before the fuel is introduced, so it's still relatively clean ambient air. As such, special filtering is not really required, not any more than say a cabin air filter on a car.
Because taking bleed air from an engine robs it of power, commercial airliners will generally use a mix of engine bleed air and recirculated cabin air for the ECS. This reduces the amount of bleed air taken from the engines, and improves their efficiency.
Where the HEPA filters become important is for filtering of the recirculated cabin air. If you were to look under the floor of a commercial airliner that's been in service for a few years, there is a lot of collected dust, dirt, hair, and grime from all the people who've sat for hours on end. Since a significant amount of the air you're breathing onboard is recirculated, the HEPA filters are important for filtering out the typical air impurities you get from having a confined space with lots of people, not necessarily from the engine bleed air.

Bleed Air is filtered using air filters. Various companies offer a lot of air filters, but High-efficiency particulate arrestance (HEPA) is a fairly common filter used to filter bleed air.
Its working is as under:

HEPA filters are composed of a mat of randomly arranged fibres. The
  fibres are typically composed of fiberglass and possess diameters
  between 0.5 and 2.0 micrometers. Key factors affecting function are
  fibre diameter, filter thickness, and face velocity. The air space
  between HEPA filter fibres is much greater than 0.3 μm. The common
  assumption that a HEPA filter acts like a sieve where particles
  smaller than the largest opening can pass through is incorrect. Unlike
  membrane filters at this pore size, where particles as wide as the
  largest opening or distance between fibres cannot pass in between them
  at all, HEPA filters are designed to target much smaller pollutants
  and particles. These particles are trapped (they stick to a fibre)
  through a combination of the following three mechanisms:

Interception, where particles following a line of flow in the air stream come within one radius of a fibre and adhere to it.
Impaction, where larger particles are unable to avoid fibres by following the curving contours of the air stream and are forced to
  embed in one of them directly; this effect increases with diminishing
  fibre separation and higher air flow velocity.
Diffusion, an enhancing mechanism that is a result of the collision with gas molecules by the smallest particles, especially
  those below 0.1 µm in diameter, which are thereby impeded and delayed
  in their path through the filter; this behaviour is similar to
  Brownian motion and raises the probability that a particle will be
  stopped by either of the two mechanisms above; it becomes dominant at
  lower air flow velocities.

Diffusion predominates below the 0.1 μm diameter particle size.
  Impaction and interception predominate above 0.4 μm. In between, near
  the most penetrating particle size (MPPS) 0.3 μm, both diffusion and
  interception are comparatively inefficient. Because this is the
  weakest point in the filter's performance, the HEPA specifications use
  the retention of these particles to classify the filter.
Lastly, it is important to note that HEPA filters are designed to
  arrest very fine particles effectively, but they do not filter out
  gasses and odor molecules. Circumstances requiring filtration of
  volatile organic compounds, chemical vapors, cigarette, pet, and/or
  flatulence odors call for the use of an activated carbon (charcoal)
  filter instead of or in addition to a HEPA filter. (ZAND)

HEPA actually looks like this :
The specifications of HEPA are as under:

HEPA filters, as defined by the DOE standard adopted by most American
  industries, remove at least 99.97% of airborne particles 0.3
  micrometers (µm) in diameter. The filter's minimal resistance to
  airflow, or pressure drop, is usually specified around 300 Pa at its
  nominal flow rate.
The specification usually used in the European Union is the European
  Norm EN 1822:2009. It defines several classes of HEPA filters by their
  retention at the given most penetrating particle size (MPPS):
  particle size (MPPS):
HEPA class    retention (total)   retention (local)
E10          >85%                 ---

E11          >95%                 ---

E12          >99.5%               ---

H13          >99.95%            >99.75%

H14          >99.995%           >99.975%

U15          >99.9995%          >99.9975%

U16          >99.99995%         >99.99975%

U17          >99.999995%        >99.9999%

The original HEPA filter was designed in the 1940s and was used in the
  Manhattan Project to prevent the spread of airborne radioactive
  contaminants. It was commercialized in the 1950s, and the original
  term became a registered trademark and a generic term for highly
  efficient filters. Over the decades filters have evolved to satisfy
  the higher and higher demands for air quality in various high
  technology industries, such as aerospace, pharmaceutical processing,
  hospitals, health care, nuclear fuels, nuclear power, and electronic
  microcircuitry (computer chips).
Today, a HEPA filter rating is applicable to any highly efficient air
  filter that can attain the same filter efficiency performance
  standards as a minimum and is equivalent to the more recent NIOSH N100
  rating for respirator filters. The United States Department of Energy
  (DOE) has specific requirements for HEPA filters in DOE regulated
  applications. In addition, companies have begun using a marketing term
  known as "True HEPA" to give consumers assurance that their air
  filters are indeed certified to meet the HEPA standard.[4]
Products that claim to be "HEPA-type", "HEPA-like", "HEPA-style" or
  "99% HEPA" do not satisfy these requirements and may not have been
  tested in independent laboratories. Some of these sub-par quality
  filters may come reasonably close to HEPA filtration, while others
  will fall significantly short, making them truly inferior.[5]

Here is the Wikipedia article

If your entire answer is a quote from somewhere else, it would be nice to give credit.

This would be a good answer if the question was "What is a HEPA filter?", but except for the unsubstantiated (HEPA) is a fairly common filter used to filter bleed air quote, it doesn't really answer the question of what kind of filters are used - can you provide any references to your statement about the type of filters used?

If you are speaking of the commercial airlines, like the 737, 757, 767, etc and Airbus equivalents, they are designed to cruise at above 30,000 feet where there (typically) is no debris to filter.
The bleed air comes from one of the Compression stages of the engine (or from the APU unit when the aircraft is on the tarmac). The bleed air is used for a lot of things (de-icing, defogging, pressurizing the potable water tanks, etc.) as well as providing air for the crew and passengers to breathe and to cool the avionics.
The air in a typical large airliner is completely changed out on the order of six times per hour. The air that comes to the passenger compartment is: half from recycled air that is filtered through a HEPA filter system to remove all bacteria and viruses (sub-micron particles) and half from the bleed air system at a temperature of over 450 deg F. The two are mixed and sent to the airplane’s air conditioning system before distribution to the cabin and to the avionics.
Recently I worked with a group to design a filter for commercial airliners. We have a demonstration model in production. That can be used by aircraft that may encounter volcanic debris/ash during flights. However, in order to be certified by the FAA for a reasonable cost, there has to be a by-pass system so that if the filter fails it can not harm the aircraft safety/operation. A commercial aircraft (or a KC-46A for example) would have two filters, one for each side.
Those filters are for particulates and are useless for smells that come from gases that mix with the air. For that one needs another filtration stage that is like what is used in chemical warfare filtration.
So, if you fly in areas that may get a lot of volcanic ash/debris, check out the new filtration system.
Enjoy your flight.

Many aircraft do not have filtration on bleed air.
This FAA publication states that bleed air is cooled, but not filtered prior to mixing with cabin air.
https://www.faa.gov/data_research/research/med_humanfacs/oamtechreports/2010s/media/201520.pdf

To reiterate, bleed air is a heterogeneous mixture of constituents
  that  may  include  gases, vapors,  smoke,  fumes,  and  mist, each of
  which is potentially associated with risk of adverse health  effect
  following exposure . It is important to note that bleed air is cooled
  but not cleaned (i .e ., filtered) before being mixed with
  recirculated cabin air.

In my experience, few aircraft (I do not fly common transport aircraft, but I do fly turbine aircraft) have filters on the bleed air.
I have heard it said that the B-787 has filters on bleed air, but the last couple of B-787 I flew on used electric compressors for cabin pressurization and had a refrigerant cycle run by electric motors for cooling.
Some aircraft may have HEPA filters, and some may have inertial separators, but not all aircraft have HEPA filters in line with bleed air.  Many have no filtration on bleed air.

The 787 is the only large commercial passenger aircraft (or airliner) that doesn't use bleed air.


text:
Once you have passed the oral portion of a checkride, do you have to retake it ever again?
I recently attempted to take my Commercial/ME/Instrument checkride. I passed the oral exam portion, but shortly after the engine started running rough. After making it through about 3-4 maneuvers and tasks, the DPE and myself called safety of flight and brought the plane back in. He did a discontinuance on my app for a new rating, but did check me off on the tasks performed. He stated that the tasks performed have a two month shelf life.
My question is, does the oral exam have the same shelf life since I passed it?
The reason this is a concern is that I have a deployment with the Guard in about two weeks. If the plane doesn't get back up and running, I'm hosed. My shelf life on the checkride stuff expires on 5/31 and I won't be back home from my deployment until early to mid-June.

As long as you know your stuff you're not "hosed" -- if you can pass it once you can pass it again! Try to go up with the same examiner - they still have to give you the whole test again, but if they remember you you'll probably get a modified oral that blows through the stuff they know you know quickly & focuses more on the stuff you didn't dig in to the first time as opposed to having to grind through the same questions all over again :)

If the plane isn't up in a week, talk to your instructor about finding another plane, possibly with another FBO.  You'll probably have to take a check out flight with them, but that sure beats waiting until mid-June.

Unfortunately, yes.  It is part of the checkride and if you don't finish it within the required time you will need to take the entire checkride again.
The commercial PTS shows the areas of operations that are included in the checkride, and the oral itself is given throughout the entire process.  What most people consider "the oral" is the examiner asking questions during the "preflight preparation" portion of the checkride.  This is where they ask the most questions because in all reality, this is where you as a pilot should be asking the most questions.
There is a note in the beginning of the PTS which talks about this:

Examiner Responsibility
The examiner conducting the practical test is responsible for
  determining that the applicant meets the acceptable standards of
  knowledge and skill of each Task within the appropriate practical
  test standard. Since there is no formal division between the “oral”
  and “skill” portions of the practical test, this becomes an ongoing
  process throughout the test. Oral questioning, to determine the
  applicant’s knowledge of Tasks and related safety factors, should be
  used judiciously at all times, especially during the flight portion of
  the  practical test. Examiners shall test to the greatest extent
  practicable  the applicant’s correlative abilities rather than mere
  rote  enumeration of facts throughout the practical test.
...

As a small aside, you don't really get two months, but rather 60 days.  This is covered in 14 CFR 61.43:

§61.43 Practical tests: General procedures.
...
(f) If a practical test is discontinued, the applicant is entitled
  credit for those areas of operation that were passed, but only if the
  applicant:
(1) Passes the remainder of the practical test within the 60-day
  period after the date the practical test was discontinued;
(2) Presents to the examiner for the retest the original notice of
  disapproval form or the letter of discontinuance form, as appropriate;
(3) Satisfactorily accomplishes any additional training needed and
  obtains the appropriate instructor endorsements, if additional
  training is required; and
(4) Presents to the examiner for the retest a properly completed and
  signed application.


text:
Can you breathe with a drop down mask under water?
Say a passenger jet lands in the ocean. Could the captain being the last person to get off the jet use the drop down dry chemical oxygen generators to breathe while checking for passengers? I know they are flimsier so depending on depth they would collapse.

I'm sure you asking about the "captain"  not the "caption." // You seemed to have answered you own question. At any real depth such face masks would collapse. // Now the drop down generators have fixed positions. Underwater in the dark, without a face mask, with all kinds of stuff floating around in the cabin, how is the captain going to find the masks going station to station? // Even with real scuba gear maybe 200 feet in depth for a limit. Once a plane has sunk to 5 feet the additional time to 200 feet would be short.

@MaxW fixed my spelling. And yeah I guess you're right. I didn't really think of all of the stuff that would be floating around either. I guess I was more I interested in does the chemical reaction still work.

You're also going to want to get out of the aircraft way before it gets to the point of your head being underwater.

Yes the gas would flow underwater for some depth. The chemical reaction is occurring in a sealed container which is mechanically triggered by pulling down on a gas mask. So the water seal on the trigger is the weak link. I'm sure that the seal is fairly weather tight so that humidity from the air doesn't get into the canister.

On airliners, there are usually portable O2 breathing equipments that could be used in this case. The gas is not generated, this is only a bottle with compressed oxygen for at least 15 mn use. It exists also different modes of distribution, including hood.

Also we don't breath oxygen, we breath air (~80% nitrogen plus ~20% oxygen). Diving with such device can be dangerous because too much oxygen and you get poisoned

Perhaps interesting: this video shows that fighter pilot life support systems can indeed be used underwater - I guess the same could be said for airline pilot masks that may also be airight. However, since you specifically refer to the drop-down masks, my answer should still be valid.

The only plausible scenario where oxygen mask would be of some help is if you had to dive to reach an exit while trapped in an air bubble.
This way breathing pure oxygen will help you to take a longer dive.

No, you cannot - at least not with the default masks.
In principle, the oxygen systems on board can all provide at least 15 mins. of oxygen, in some of the worst conditions (indeed, that's what they're designed to do). However, their sole purpose is to make high altitude air breathable. The key principle here is partial pressure. Basically, the partial pressure of a gas is the fraction of a certain gas in a gas mixture times the ambient pressure. Since normal air consists of about 21% oxygen, the partial pressure of oxygen at sea level is 0.21 atm (atmosphere). If the partial pressure of oxygen is too low, your lungs actually lose oxygen to the atmosphere when you breathe - much like a deflating balloon.
When the cabin pressure drops, the partial pressure of oxygen drops proportionally. In that case, oxygen masks are provided. They do not raise the pressure of the air you breathe in, but raise the partial pressure of oxygen by filling your mask with oxygen. If the cabin pressure would drop to 0.2 atm, and you would be given 100% oxygen, the partial pressure of oxygen would be 0.2atm, which is about the same as at sea level - perfectly survivable. The mask as such does not need to be airtight - it just needs to make sure that there's enough oxygen flowing into your mask to displace all the useless nitrogen in the air. Indeed, the mask you will see on airplanes are generally flimsy, plastic masks.
Under water, these masks are not sufficient at all. They will probably turn into a frothy, bubbly mess of a water/oxygen mixture, especially when the aircraft is filling up with water, due to strong currents. So, you would have to wait for the currents to diminish, and then hold your oxygen mask in such a way that no water will enter it - this probably means you will have to face upwards all the time.
Of course, you can get creative (pull the mask of and breathe from the tube), or luck out with a high quality mask that happens to work underwater. But I'm afraid that as soon as your plane is sinking, it's too late to play the hero, and your best bet would be to get out and at least save your own life.

It is a chemical reaction. So yes, if contained it could provide oxygen under water (provided the reaction did not react with the water). However, it would not work for the reasons already mentioned in the comments and the infeasible logistics of a hollywood captain single-handedly saving his passengers at the last second ;-)
https://en.wikipedia.org/wiki/Emergency_oxygen_system#Mechanism
https://en.wikipedia.org/wiki/Chemical_oxygen_generator

It depends on how much oxygen is provided by the mask, i.e. what the flow rate is.
I guess masks for pilots should be independent from ambient air at any altitude for the case that there's smoke in the cockpit.
So yes, they would provide enough air for breathing at sea level, or even slightly under water. But those masks are in the cockpit and not mobile.
Oxygen masks for passengers don't provide all the air they breathe, they just add some oxygen to the ambient air.
Have a look at this diagram, which shows which fraction of oxygen in air at certain altitudes correspond to which at sea level:

(This uses the given percentages and the simple common barometric formula, other sources may show other curves)
It would be fine if passengers are kept somewhere in the yellow region, as e.g. drowsiness wouldn't matter for them, just sitting around.
At an altitude of about 12km/ 40,000ft, the passengers should get air with maybe 50% oxygen, 20% from the ambient, 30% from the mask.
Now, imagine you are under water and try to breathe from the oxygen masks only. You will have to cut off the mask and breathe from the tube. The flow rate from this pipe is just 30% of the usual flow rate, so you have to breathe very slowly. This will be a problem, though the amount of oxygen from the tube would be fine.
Physical stress like diving through the aircraft and pulling out passengers would increase the need for oxygen drastically and then, even the pure oxygen from the tubes would not be enough.
You may put several tubes into your mouth, if you manage to do that.
Finally, the gas flow from chemical oxygen generators decreases after activation, and comes to rest after a few minutes, so this wouldn't work if the masks were already deployed at high altitude.
I don't know about the mobile oxygen devices for the crew. If they allow to breathe independent from ambient air, they would work under water. But I guess, they also only enrich the air with oxygen, may be more than the passenger's masks.

Too bad the chart isn't it feet... I got very confused for a moment when I looked at 8000 (typical airline pressure altitude) saw it would leave the passengers unconscious :P

@JeffBridgman: the bottom x-axis is in m, but the top is in ft!

In addition to the discussion of the physical ability to use the mask to deliver oxygen under water - it is worth noting that breathing pure oxygen in a high pressure environment results in oxygen toxicity.
In short, oxygen at high concentrations is increasingly poisonous to our nervous system and pulmonary system as atmospheric pressure increases. This makes your example question an even more terrifying prospect if the aircraft is sinking rapidly.
Now, if faced with the choice of drowning or rolling the dice with toxicity, I guess I'd try the mask...

Not really. The text you linked says 100% oxygen at sea level causes pain after 1h and problems after 24h. Even if this happens earlier at some higher pressure under water, I wouldn't mind this in the given scenario.

Well, the fact that you would take the risk isn't surprising, I would too in this scenario. I think you may be confusing my point though. The oxygen in the mask is 100% concentration. If compressed air (21% O) at depth is the same risk as breathing 100% O at sea level for 1 hour, then breathing 100% O at depth would be very dangerous very quickly.

Then can you explain how I survived daily 2 hour compression dives in pure O2 in a hyperbaric chamber for a week in the hospital? Only pain I experienced was from the gaping wound in my leg because they couldn't run the IV with my pain meds into the chamber.

I'm not really saying anything controversial here - this is the reason people don't scuba dive with oxygen. If you are carefully monitored in a chamber then you aren't plummeting to the bottom in an aircraft sucking pure oxygen uncontrolled!  http://www.elitedivingagency.com/articles/scuba-tank-gas-mixture-divers-use/

Yeah, I know O2 tox is a problem and I'm not sure what the difference is with HBO. I think I might post a question about it on physics SE since I've long wondered about that. I'm just thinking if the OP is talking about escaping from an aniraft underwater that it probably wouldn't be deep enough for long enough to matter.

It really just depends on how deep you get. If you are deep enough it would be pretty short amounts of time. As far as HB chambers are concerned, its primary use in your case was to treat bacterial infection with oxygen exposure. It may be an answer just as simple as "it is worth the poisoning". Similar in a way to chemotherapy for cancer patients. Yes, it is poison, but it is helping you. As far as why you didn't have symptoms, it could have to do with the exact pressure settings they had you at. I'm sure they watched your levels closely and rode the healthy edge! (Hope you are all healed!)

Oxygen toxicity is only relevant if the partial pressure rises well above the equivalent of 100% oxygen at sea level. The masks can't provide that much oxygen.

sadly the URL linked is 404 in 2021 :(


text:
Is trimming aircraft to relieve pilot of applying force on control stick/Pedal still applicable?
I know that historically pilots used to trim an aircraft to relieve continuous application of force during climb/cruise/descent, and at that trim tabs existed on control surfaces (elevator, ailerons, etc) which could be used to hold the position of the control surface without the pilot applying any force. But now, we don't usually have trim tabs, and with fly-by-wire systems forces have been reduced on the pilot.
Does trimming do anything other than reduce pilot workload? Also:

Do modern aircraft still follow this concept of trim to reduce pilot's continuous force on the flight controls?
Apart from pilot workload and fuel efficiency (I know that trimming an aircraft can produce drag), what other benefits does trim offer?
Without trim tabs, how is trimming accomplished?

Many of us are still flying planes built in the '60s and '70s, if not before, so 'modern aircraft' and fly-by-wire are concepts that apply to a very limited range of pilots.

Trimming a plane is like doing wheel alignment on your car. Sure, you can drive an un-aligned car but having to constantly hold the steering wheel left while driving in a straight line gets annoying (and dangerous) after a while.

You may find relevant pieces of answers in this question

Almost all airplanes have trim (I'm fairly certain that the Wright Flyer didn't, so I can't say all airplanes do), but a lot of newer designs don't use trim tabs because they are less aerodynamically efficient than alternative designs.
For instance, the Falcon 50 & 900 that I fly doesn't have a single trim tab on it.  Normally the flight controls are moved by hydraulics and a small electrical actuator is used to adjust the position of the aileron and rudder for trim purposes.  Pitch trim is accomplished by moving the front of the entire horizontal stabilizer in order to adjust the angle and amount of lift produced by the tail.  This is done so that the elevator can be neutralized and not create the additional drag caused by being in the airflow.

On FBW airplanes, they may or may not have manual trim that is used (under normal circumstances) by the pilot.   Trimming is still taking place on FBW airplanes without manual trim, but it is simply automated.
Boeing typically designs their FBW airplanes so that they behave like a "normal" airplane, and require the pilot to trim in order to relieve the control forces.  This is all completely artificial though, programmed simply to give feedback to the pilot.
Airbus on the other hand doesn't give any feedback to the pilot through the side stick so there are no control forces to relieve.   When you release the side stick, it centers and the aircraft maintains its current pitch and bank angle.  In this case, the autopilot automatically trims the airplane for the current conditions, and the pilot doesn't need to worry about it.

It might be worth noting that while the trim in Airbus is normally operated automatically, the trim wheel has direct hydraulic link to the stabilizer and is used as backup for case of total electrical failure (which I've never heard of happening in practice).

This is control surface trimming. It might also be useful to mention weight-based trimming such as tank trimming, which is even more aerodynamically efficient as it doesn't add induced drag from changing the angle of attack of control surfaces.

Some light airplanes also have a horizontal stabilizer that pivots, rather than using a trim tab. Mooneys, for example, use a jack screw attached the the pitch control system in the cockpit and to the horizontal stabilizer to change the angle of incidence of tail, thus changing the pitch trim (by changing the angle of attack and, thus, lift [negative lift, actually] generated by the tail).

In reference to item 1 of the question, it's not only to reduce the pilot's continuous force on the flight controls but also that of the autopilot. For example, you're straight and level with the autopilot holding altitude, and as the flight progresses your center of gravity is moving forward due to fuel burn. The autopilot compensates with an up-elevator force. On 747-100s -200s there's a gauge that shows you how much up-elevator the autopilot is commanding. So, if you're about to disengage the autopilot, you'd best glance down at that gauge to anticipate the control force you're going to need. If you're in cruise, you may still want to keep an eye on it and add appropriate trim manually to save a little fuel. If you're lazy, you can ignore it, and when the up-elevator requirement reaches a certain point, the autopilot will trim it out.

from my time in simulators, that can really unexpectedly bite you. Disengaging the autopilot and suddenly the nose is pointing 30 degrees down on final...

@HCBPshenanigans See http://terryliittschwager.com/hajj4contest.php for a humorous tale involving such.

Trims function is to balance the downward directed lift from the horizontal stab against the upward directed lift from the wing.  Obviously, the lift generated by the wing varies with airspeed, and as a consequence we trim for an airspeed.  The other consequence is we trim for 0 control column/stick deflection, that is to say the balance of forces we trim for assumes no control input.  We do this for stability.
The perception we get from that is that we trim to reduce control forces, and while that conclusion is true, I argue that it is a consequence to what we are really doing.  With that said, the control column force reduction is absolutely essential, particularly when flying a high performance airplane capable of a wide range of speeds.
For FBW systems, the need to balance the lift on the trim and wing is still necessary and so the need for trim still exists.  The trim won't have an impact on control forces in this case, but will adjust the need for deflection of the stick just as in a traditional control column or stick.
For larger airplanes without a trim tab, the horizontal stabilizer becomes a horizontal stabilator in which the entire horizontal surface moves.  The whole surface rotates to change its angle of attack and the associated change in lift is how trim is accomplished.
For the other trims (aileron and rudder) in larger airplanes these can be implemented in the hydraulic actuators that actually move those control surfaces. These would cause a constant offset deflection from the control input.

Trim still exists on new airplanes.   I don't know where you got the idea that planes don't have trim tabs, or that FBW eliminated this.  Any sources or evidence to support your claim?
(This article describes the trim of the 787)

Some jets replace trim-tabs with a movable stabilizer, which might be what he's referring to?

@ abelenky: Not many modern aircraft don't have trim tabs Yup, this is part of sub-question 3. Pitch trim is done by movable stabilizer than how roll trim & yaw trim are done?

@egid Airbus doesn't use trim tabs.

@Lnafziger not even for aileron trim? Guess I never stared hard enough!

It's been around 25 years since my initial ground school on the 747-100 and -200, but as I remember, aileron and and rudder trim are handled by the hydraulics holding those control services to whatever trim setting you select. Both ailerons and rudders are split: there are inboard and outboard ailerons, top and bottom rudders. I seem to remember that you're trimming only the bottom rudder and the inboard ailerons, but I might not have that correct.

Just as a matter of curiosity, 727-100s had 3 trim switches. Each control yoke had a fast-trim switch that really moved. Then on the center console there was a slow-trim switch that could be reached by either pilot. If you wanted a really fine adjustment, you could move the large trim wheel on the center console by hand.

Yes, trim still exists, it's a really useful feature! Imagine flying from New York to London while gently pulling at the column for 6 hours in order for the aeroplane to maintain its flight path, that would be most inconvenient.
Trim tabs were/are used back in the days when aeroforces provided the feel forces for the pilot, nowadays the planes are too fast and big and irreversible hydraulic actuators move the control surfaces. This means that feel must now be produced by mechanical springs and dampers.
And this arrangement also provides a convenient way to introduce trim: just adjust the neutral point of the feel spring. Picture the feel spring with the stick attached to one end, and the other end is connected to the aircraft structure via an adjustable screw-jack. Push the trim button, and the jack starts to turn - a nut on its shaft shifts until the feel spring is not extended anymore.